Sponge



FIG. 1 is a perspective view of a sponge showing my new design;

FIG. 2 is a side elevation view of my sponge design which appears the same in elevation when viewed from any direction;

FIG. 3 is a top plan view thereof; and,

FIG. 4 is a bottom plan view thereof. 

The ornamental design for a sponge, as shown and described. 